In this paper we present photoluminescence, photoreflectance, and absorbance measurements on silicon
samples with b-FeSi2 precipitates, as structurally characterized in the first part of this paper @M. G. Grimaldi
et al., Phys. Rev. B 66, 085319 (2002). By comparing the photoluminescence measurements in different
experimental conditions and with excitation energy above and below the silicon threshold, by considering the
direct gap estimations by photoreflectance and absorption, we argue that the 1.54 mm photoluminescence peak
in the spectra is produced by an indirect transition in the disc-shaped precipitates. However, the latter ones are
predicted to be the most efficient configuration, acting as a trapping well for carriers generated in the silicon
matrix, and displaying a high structural quality with no dangling bonds at the b-FeSi2 /Si interface. Our simple
model, based on band lineup at the interface, is also able to explain the temperature quenching of the photoluminescence
peak.

In this paper we present photoluminescence, photoreflectance, and absorbance measurements on silicon
samples with b-FeSi2 precipitates, as structurally characterized in the first part of this paper @M. G. Grimaldi
et al., Phys. Rev. B 66, 085319 (2002). By comparing the photoluminescence measurements in different
experimental conditions and with excitation energy above and below the silicon threshold, by considering the
direct gap estimations by photoreflectance and absorption, we argue that the 1.54 mm photoluminescence peak
in the spectra is produced by an indirect transition in the disc-shaped precipitates. However, the latter ones are
predicted to be the most efficient configuration, acting as a trapping well for carriers generated in the silicon
matrix, and displaying a high structural quality with no dangling bonds at the b-FeSi2 /Si interface. Our simple
model, based on band lineup at the interface, is also able to explain the temperature quenching of the photoluminescence
peak.